1. Field of the Invention
The present invention relates to charged particle beam exposure systems and methods and, more particularly, to a charged particle beam exposure system and method for exposing a desired pattern on a surface of an object as a result of raster scanning of charged particle beams, while controlling each of the plurality of charged particle beams such that the charged particle beams as a whole form a beam bundle having the desired exposure pattern.
2. Description of the Related Art
The present invention uses some of the teachings of the U.S. Pat. No. 5,369,282 and U.S. patent application Ser. No. 08/241,409 filed May 11, 1994, which are herein incorporated by reference.
With the advancement in the art of fine lithographic patterning, recent integrated circuits are formed with such a high integration density that they are now used commonly and widely in industries including computers, telecommunications, system control, and the like. Looking back at the history of dynamic random access memories, for example, it will be noted that the dynamic random memories have increased the integration density as represented in terms of storage capacity of information, form 1 Mbits to 4 Mbits, from 4 Mbits to 16 Mbits and from 16 Mbits to 64 Mbits. Currently, dynamic random access memories having a storage capacity of 256 Mbits or 1 Gbits are studied intensively. In correspondence with such an increase in the integration density, extensive studies are in progress for developing the art of so-called charged particle beam exposure that uses a charged particle beam such as an electron beam for exposing fine patterns on an object. By using such a charged particle beam, it is possible to expose a pattern having a size of 0.05 xcexcm or less, with an alignment error of 0.02 xcexcm or less.
On the other hand, conventional charged particle beam exposure systems have suffered from the problem of low throughput of exposure, and there has been a pessimistic atmosphere prevailing among those skilled in the art about the production of integrated circuits by means of such a charged particle beam exposure system. It should be noted that the conventional charged-particle-beam exposure systems have used a single charged particle beam for the exposure and it has been necessary to draw a desired pattern on the object such as a substrate by a single stroke of the charged article beam.
On the other hand, most of such pessimistic observations addressing negative predictions about the future of charged-beam-exposure system and method, are not well founded, as is typically demonstrated by the inventors of the present invention who have succeeded in constructing a block exposure system and a BAA (blanking aperture array) exposure system that provide a throughput of as much as 1 cm2/sec. With the high throughput of 1 cm2/sec thus achieved, the main disadvantage of the charged-particle-beam exposure system and method is substantially eliminated. Now, it is thought that the charged-particle-beam exposure system and process are superior to any other conventional exposure systems in terms of high resolution, small alignment error, quick turn around time and reliability.
As already noted, it is particularly essential for a charged-particle-beam exposure system to have a high exposure throughput, and block exposure process or BAA process has been developed for clearing the requirement of high exposure throughput. Hereinafter, a BAA exposure system proposed previously by the inventors of the present invention will be described briefly. For the sake of simplicity, the description hereinafter will be made for an electron beam exposure system, while the present invention is by no means limited to an electron beam exposure system but is applicable to any other charged particle beam exposure systems such as an ionic beam exposure system that uses a focused ionic beam.
In a BAA exposure system, a plurality of electron beams are produced such that the plurality of electron beams are produced such that the plurality of electron beams as a whole form a desired electron beam bundle with a shape corresponding to a pattern to be exposed on an object. Thereby, each of the plurality of electron beams is turned on and off individually according to the desired pattern to be exposed. Thus, each time the exposure pattern is changed, a different set of electron beams are turned on. While being exposed by the electron beams on the object, which may be a substrate, the object is moved, together with a stage on which the object is supported while deflecting the electron beams back and forth by activating a deflector.
In order to produce the foregoing plurality of electron beams, the BAA exposure system employs a BAA mask that is a plate formed with a number of rectangular apertures arranged in rows and columns for shaping a single electron beam incident thereto. Each of the apertures carries a pair of electrodes on opposing edges, wherein one of the electrodes is set to a ground potential level while the other of the electrodes is supplied with a control signal that changes the level between the ground level and a predetermined energization level. In response to the energization of the electrodes on the BAA mask, the path of the electron beam through the aperture is deflected and the arrival of the electron beam upon the object is controlled accordingly. In other words, the electron beams are turned on and off on the object in response to the control signal applied to the electrodes of the apertures on the BAA mask. It should be noted that the control signals applied to the apertures on the BAA mask represent a pattern of the electron beams produced by the BAA mask, and the control signals are changed in synchronization with a raster scanning of the surface of the object by the electron beam bundle. As a result of the raster scanning, the object is exposed along a band or zone.
In such conventional BAA exposure systems and methods, there are still various problems to be overcome, such as further improvement of the exposure throughput including improvement of data transfer rate and data compression, improvement in the precision of the exposed patterns including optimization of exposure dose and improvement of resolution when expanding exposure data into bit map data, uniform distribution of the electron beam intensity throughout the substrate, improved data processing such as expansion and transfer of the exposure dot data, positive on-off control of the electron beam, easy maintenance of the BAA mask, exposure of large diameter wafers, improvement of electron optical systems, and easy switching between a BAA exposure mode and a block exposure mode, and the like.
Accordingly, it is an object of the present invention to provide a novel and useful charged-particle-beam exposure system and method wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a charged-particle-beam exposure method and system for exposing versatile patterns on an object by means of a charged particle beam that forms an exposure dot pattern, in which the creation of dot pattern data representing the exposure dot pattern and the exposure of the object by means of the charged particle beam can be achieved separately.
Another object of the present invention is to provide a charged-particle-beam exposure method and system that is capable of holding a large amount of dot pattern data representing the exposure dot pattern and that can control a blanking aperture array based upon the dot pattern data at a high speed for producing a charged particle beam bundle including a number of charged particle beams in correspondence to each dot of the exposure dot pattern.
Another object of the present invention is to provide a method for exposing a pattern on an object by means of a charged particle beam, comprising the steps of:
shaping a charged particle beam into a plurality of charged particle beam elements forming collectively a charged particle beam bundle having a desired pattern in response to exposure date;
calculating a beam correction to be applied upon said charged particle beam elements for compensating for a beam distortion when exposing said desired pattern on said object, as a function of said exposure data, said step of calculation being conducted in response to a correction clock; and
exposing said desired pattern upon said substrate by radiating said charged particle beam bundle upon said object in response to an exposure clock;
said step of exposing comprising the steps of:
setting a frequency of said exposure clock based upon a sensitivity of a resist provided on said object and a current density of said charged particle bean elements; and
emitting said charged particle beam elements forming said charged particle beam bundle upon said object in response to said exposure clock, with said beam correction applied to said charged beam elements;
wherein said correction clock is synchronized to said exposure clock and held at a substantially constant, predetermined frequency when changing the frequency of said exposure clock in said step of setting the frequency of said exposure clock.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a desired pattern on an object, comprising:
a charged particle beam source for producing a charged particle beam and emitting the same along a predetermined optical axis;
beam shaping means provided on said optical axis so as to interrupt said charged particle beam, said beam shaping means carrying thereon a plurality of apertures for shaping said charged particle beam into a plurality of charged particle beam elements collectively forming a charged particle bundle, each of said apertures carrying switching means for selectively turning off said charged particle beam element in response to exposure data;
beam focusing means for focusing each of said charged particle beam elements forming said charged particle beam bundle upon said object;
deflection means for deflecting said charged particle beam elements collectively over a surface of said object in response to a deflection control signal supplied thereto;
deflection control means supplied with deflection data for producing said deflection control signal;
beam correction means for calculating a beam correction to be applied to said electron beam element as a function of said exposure data for compensating for a beam distortion, said beam correction calculation means carrying out said calculation in response to a correction clock;
exposure control means for conducting an exposure of said charged particle elements in response to an exposure clock; and
clock control means supplied with control data indicative of a current density of said charged particle beam elements and a sensitivity of said electron beam resist, for producing said exposure clock and said correction clock, such that said exposure clock has a clock speed determined as a function of said control data, said clock control means further holding said correction clock substantially constant at a predetermined frequency irrespective of the frequency of said exposure clock.
According to the present invention, it is possible to conduct the development of exposure data into exposure dot data and the exposure of the pattern on the object at respective timings. Thereby, the exposure throughput is no longer limited by the data expansion of the exposure data to the exposure dot data and a high exposure throughput can be achieved. Further, it is possible to hold or save a large amount of exposure dot data in the primary storage device that may be a hard disk device. By using a non-volatile storage device such as a hard disk for the primary storage device, it is possible to examine the exposure data in the form of exposure dot data. Further, such exposure dot data can be used repeatedly in the production of a semiconductor device. Although the primary storage device may have a limited access speed, it should be noted that the exposure dot data is supplied to the beam shaping means, which is a blanking aperture array, at high speed from the secondary storage device.
In a preferred embodiment of the present invention, two or more high speed memory devices are used for the secondary storage device each having a storage capacity smaller than the primary storage device.
Another object of the present invention is to provide a charged particle beam exposure system and method wherein a high precision exposure is guaranteed even when the setting for the current density of the electron beam or the sensitivity of the electron beam resist is changed.
Another object of the present invention is to provide a method for exposing a pattern on an object by means of a charged particle beam, comprising the steps of:
shaping a charged particle beam into a plurality of charged particle beam elements forming collectively a charged particle beam bundle having a desired pattern in response to exposure data;
calculating a focusing error correction and an aberration correction to be applied upon said charged particle beam elements when exposing said desired pattern on said object, as a function of said exposure data, said step of calculation being conducted in response to a correction clock; and
exposing said desired pattern upon said object by radiating said charged particle beam bundle upon said object;
said step of exposing comprising the steps of:
setting an exposure clock speed based upon a sensitivity of an electron beam resist provided on said object and a current density of said charged particle beam elements; and
emitting said charged particle beam elements forming said charged particle beam bundle upon said object in response to said exposure clock, with said focusing error correction and said aberration correction;
wherein said correction clock is held in the vicinity of a predetermined clock speed when changing a clock speed of said exposure clock in said step of setting the exposure clock speed.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a desired pattern on an object, comprising:
a charged particle beam source for producing a charged particle beam and emitting the same along a predetermined optical axis;
beam shaping means provided on said optical axis so as to interrupt said charged particle beam, said beam shaping means carrying thereon a plurality of apertures for shaping said charged particle beam into a plurality of charged particle beam elements collectively forming a charged particle bundle, each of said apertures carrying switching means for selectively turning off said charged particle beam element in response to exposure data;
beam focusing means for focusing each of said charged particle beam elements forming said charged particle beam bundle upon said object;
deflection means for deflecting said charged particle beam elements collectively over a surface of said object in response to a deflection control signal supplied thereto;
deflection control means supplied with deflection data for producing said deflection control signal;
beam correction means for calculating a correction to be applied to said electron beam element as a function of said exposure data, said beam correction calculation means carrying out the calculation in response to a correction clock;
exposure control means for conducting an exposure of said charged particle elements in response to an exposure clock; and
clock control means supplied with control data indicative of a current density of said charged particle beam elements and a sensitivity of said electron beam resist, for producing said exposure clock and said correction clock, such that said exposure clock has a clock speed determined as a function of said control data, said clock control means further holding said correction clock substantially constant irrespective of said exposure clock.
According to the invention of the present embodiment, one can guarantee a necessary exposure dose by changing the exposure clock as a function of the resist sensitivity and the current density. On the other hand, the analog signal supplied to the deflection means, which includes a main deflector and a sub-deflector, changes generally linearly with time, and the problem of the exposure beam failing to hit the desired point on the substrate is effectively eliminated.
Another object of the present invention is to provide a charged particle beam exposure system and method that is capable of exposing an object by charged particle beams produced by a BAA mask with a uniform electron beam intensity irrespective of the location of the apertures on the BAA mask that are used for shaping the electron beams.
Another object of the present invention is to provide a method for exposing a pattern on an object, comprising the steps of:
shaping a charged particle beam into a plurality of charged particle beam elements forming collectively a charged particle beam bundle having a desired pattern in response to exposure data;
exposing a desired pattern upon said object by radiating said charged particle beam bundle upon said object;
said step of beam shaping comprising the steps of:
activating a plurality of apertures provided on a beam shaping mask for shaping said charged particle beam, such that a predetermined number of said apertures are activated each time as a unit, each of said apertures including a deflector for deflecting a charged particle beam element passing therethrough in response to an activation of said aperture, said predetermined number of apertures thereby producing a plurality of charged particle beam elements equal in number to said predetermined number; and
detecting the intensity of said predetermined number of charged particle beam elements on said object;
said step of activating said plurality of apertures being conducted such that the intensity of said charged beam elements, produced as a unit, is equal to the intensity of said charged particle beam elements of other units, by optimizing an energization of said deflectors on said predetermined number of apertures.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a pattern on an object, comprising:
a charged particle beam source for producing a charged particle beam and emitting the same along a predetermined optical axis;
beam shaping means provided on said optical axis so as to interrupt said charged particle beam, said beam shaping means carrying thereon a plurality of apertures for shaping said charged particle beam into a plurality or charged particle beam elements collectively forming a charged particle bundle;
switching means for selectively turning off said charged particle beam element in response to a control signal;
driving means for driving said switching means on said beam shaping means by supplying thereto said control signal in response to exposure data;
beam focusing means for focusing each of said charged particle beam elements forming said charged particle beam bundle upon said object;
detection means for detecting the intensity of said charged particle beam elements on said object;
correction means for controlling said driving means such that said driving means supplies said control signal to said switching means with an offset added thereto, said correction means evaluating said offset in response to the intensity of said charged particle beam elements detected by said detection means, such that a group of charged particle beam elements including a predetermined number of charged particle beam elements therein has an intensity that is substantially identical to the intensity of other charged particle beam elements forming other groups, each of said other groups including said charged particle beam elements in number identical to said predetermined number.
According to the present invention as set forth above, the intensity of the charged particle beam elements is detected for each unit or group including a predetermined number of charged particle beam elements, wherein the intensity of the charged particle beam elements is adjusted for each unit in response to the detected beam intensity on the object, by adjusting the energization of the switching means or deflectors cooperating with each of the apertures, such that the beam intensity is substantially uniform over the entire surface of the object. Thereby, the problem of the exposure dots shaped by the apertures on the marginal area of the BAA mask is substantially eliminated, and a high precision exposure becomes possible.
Another object of the present invention is to provide a charged particle beam exposure system and method that improves the data transfer rate and hence the exposure throughput by compressing the dot pattern data during the process of data transfer.
Another object of the present invention is to provide a method for exposing a pattern on an object by means of a charged particle beam, comprising the steps of:
producing a plurality of charged particle beam elements in the form of dot pattern data, said plurality of charged particle beam elements being produced simultaneously as a result of shaping of a single charged particle beam by a mask, said mask carrying a plurality of beam shaping apertures arranged in rows and columns on a mask area;
focusing said plurality of charged particle beam elements upon an object; and
scanning a surface of said object by means of said plurality of charged particle beam elements in a first direction;
said step of producing the plurality of charged particle beam elements includes the steps of:
dividing said dot pattern data into a plurality of data blocks each corresponding to a rectangular area on said beam shaping mask, said rectangular area having a size in a second direction perpendicular to said first direction such that said size is smaller than a size of said mask area in said second direction;
providing Identification codes to said data blocks for discriminating said data blocks from each other, such that identical data blocks have an identical identification code;
storing said data blocks respectively in corresponding dot memories, together with said discrimination codes corresponding to said data blocks;
reading out said data blocks from said dot memories consecutively by specifying said identification codes consecutively; and
shaping said single charged particle beam by said beam shaping mask into said plurality of beam shaping beam elements in response to said data blocks read out from said dot memories.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a pattern on an object, comprising:
beam source means for producing a charged particle beam and for emitting the same along an optical axis in the form of a charged particle beam toward an object;
beam shaping means disposed on said optical axis so as to interrupt said primary charged particle beam, said beam shaping means carrying on a mask area thereof a plurality of apertures each supplied with exposure dot data representing a dot pattern to be exposed on said object, said apertures thereby shaping said charged particle beam into a plurality of charged particle beam elements in response to said exposure dot data, said plurality of charged particle beam elements as a whole forming a charged particle beam bundle;
focusing means for focusing each of said charged particle beam elements in said charged particle beam bundle upon said object with a demagnification;
scanning means for scanning a surface of said object by said charged particle beam elements in a first direction;
a dot memory for storing dot pattern data for data blocks each corresponding to a group of exposure dots to be formed on a rectangular area on said object, said rectangular area having a size on said object, in a second direction perpendicular to said first direction, to be equal to or smaller than a size of said mask area projected upon said object and measured in said second direction;
a code memory for storing codes each specifying one of said data blocks;
block addressing means for addressing, based upon said codes read out from said code memory, said dot memories consecutively from a first address to a last address of a data block specified by said code; and
code memory control means for reading said codes from said code memory consecutively in the order of exposure.
According to the present invention set forth above, the same exposure data is used repeatedly by specifying the codes. It should be noted that the same data block has the same code. Thereby, the amount of the dot pattern data is substantially reduced. It should be noted that such a reduction in the amount of data decreases the duration of data transfer, and the throughput of exposure is improved substantially.
Another object of the present invention is to provide a charged particle beam exposure method and system that are capable of exposing a pattern on an object at a high speed, without requiring particular data processing with respect to pattern width or contour of the exposed pattern when conducting a minute adjustment of the exposed pattern.
Another object of the present invention is to provide a method and system for exposing an exposure pattern on an object by a charged particle beam, comprising the steps of:
shaping a charged particle beam into a plurality of charged particle beam elements in response to first bitmap data indicative of an exposure pattern, such that said plurality of charged particle beam elements are selectively turned off in response to said first bitmap data;
focusing said charged particle beam elements upon a surface of an object; and
scanning said surface or said object by said charged particle beam elements;
said step of shaping including the steps of:
expanding pattern data of said exposure pattern into second bitmap data having a resolution of n times (nxe2x89xa72) as large as, and m times (mxe2x89xa71) as large as, a corresponding resolution of said first bitmap data, respectively in X- and Y-directions;
dividing said second bitmap data into cells each having a size of 2n bits in said X-direction and 2m bits In said Y-direction; and
creating said first bitmap data from said second bitmap data by selecting four data bits from each of said cells, such that a selection of said data bits is made in each of said cells with a regularity in said X- and Y-directions and such that the number of rows in said X-direction and the number of columns in said Y-direction are both equal to 3 or more.
According to the present invention, it becomes possible to achieve a fine adjustment of the exposure pattern by using the first bitmap data without considering the effect of pattern width or conducting a processing along the contour of the pattern boundary. Thereby, the processing speed and hence the exposure throughput increases substantially.
Another object of the present invention is to provide a BAA exposure system having a BAA mask wherein the deflection of the electron beam elements is made in the same direction throughout the BAA mask.
Another object of the present invention is to provide a BAA exposure system having a BAA mask wherein the resistance and capacitance of wiring used for carrying drive signals to the electrostatic deflectors provided on the BAA mask, are optimized with respect to the timing of turning on and turning off the apertures of the BAA mask.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a pattern on an object, comprising:
beam source means for producing a charged particle beam;
beam shaping means for shaping said charged particle beam to produce a plurality of charged particle beam elements in accordance with exposure data indicative of a dot pattern to be exposed on said object;
focusing means for focusing said charged particle beam elements upon a surface of said object; and
deflection means for deflecting said charged particle beam elements over said surface of said object;
said beam shaping means comprising:
a substrate formed with a plurality of apertures for shaping said charged particle beam into said plurality of charged particle beam elements;
a plurality of common electrodes provided on said substrate respectively in correspondence to said plurality of apertures, each of said plurality of common electrodes being provided in a first side of a corresponding aperture; and
a plurality of blanking electrodes provided on said substrate respectively in correspondence to said plurality of apertures, each of said plurality of blanking electrodes being provided in a second, opposite side of a corresponding aperture on said substrate.
Another object of the present invention is to provide a beam shaping mask for shaping a charged particle beam into a plurality of charged particle beam elements, comprising:
a substrate formed with a plurality of apertures for shaping said charged particle beam into said plurality of charged particle beam elements;
a plurality of common electrodes provided on said substrate respectively in correspondence to said plurality of apertures, each of said plurality of common electrodes being provided in a first side of a corresponding aperture; and
a plurality of blanking electrodes provided on said substrate respectively in correspondence to said plurality of apertures, each of said plurality of blanking electrodes being provided in a second, opposite side of a corresponding aperture on said substrate.
Another object of the present invention is to provide a process for fabricating a beam shaping mask for shaping a charged particle beam into a plurality of charged particle beam elements, comprising the steps of:
providing a plurality of conductor patterns on a surface of a substrate with respective thicknesses such that at least one of said conductor patterns has a thickness that is different from the thickness of another conductor pattern; and
providing a ground electrode and a blanking electrode on said substrate respectively in electrical contact with said conductor patterns, said ground electrode and said blanking electrode forming a deflector for deflecting said charged particle beam elements.
According to the present embodiment set forth above, the beam shaping mask causes a uniform deflection when turning off the charged particle beam, over entire area of the mask, and the problem of leakage of the deflected charged particle beam elements upon the reversal deflection upon the blanking of the charged particle beam is successfully eliminated. Further, by optimizing the thickness and hence the resistance of the conductor patterns on the beam shaping mask, it is possible to adjust the timing of activation of the individual electrostatic deflectors formed on the beam shaping means for selectively turning off the charged particle beam elements.
Another object of the present invention is to provide a BAA exposure system in which maintenance of the BAA mask is substantially facilitated.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a pattern on an object by a charged particle beam, comprising:
beam source means for producing a charged particle beam, said beam source means emitting said charged particle beam toward an object on which a pattern is to be exposed, along an optical axis;
beam shaping means for shaping said charged particle beam to produce a plurality of charged particle beam elements in accordance with exposure data indicative of a dot pattern to be exposed on said object;
focusing means for focusing said charged particle beam elements upon a surface of said object; and
deflection means for deflecting said charged particle beam elements over said surface of said object;
said beam shaping means comprising:
a beam shaping mask carrying thereon a plurality of apertures for producing a charged particle beam element by shaping said charged particle beam and a plurality of deflectors each provided in correspondence to one of said plurality of apertures, said beam shaping means further including a plurality of electrode pads each connected to a corresponding deflector on said beam shaping means;
a mask holder provided on a body of said charged particle beam exposure system for holding said beam shaping mask detachably thereon, said mask holder comprising: a stationary part fixed upon said body of said charged particle beam exposure system; a movable part provided movably upon said stationary part such that said movable part moves in a first direction generally parallel to said optical axis and further in a second direction generally perpendicular to said optical axis, said movable part carrying said beam shaping mask detachably; a drive mechanism for moving said movable part in said first and second directions; and
a contact structure provided on said body of said charged particle beam exposure system for contacting with said electrode pads on said beam shaping mask, said contact structure including a base body and a plurality of electrode pins extending from said base, said of said electrode pins having a first end connected to said base body of said contact structure and a second, free end adapted for engagement with said electrode pads on said beam shaping mask.
According to the construction of the present embodiment, particularly the construction of the beam shaping mask held on the mask holder and the construction of the cooperating contact structure, it is possible to dismount the BAA mask easily, without breaking the vacuum inside the electron beam column. Thus, the time needed for maintenance of the BAA mask is substantially reduced, and the throughput of exposure increases substantially. Further, the BAA exposure system of the present embodiment is advantageous in the point that one can use various beam shaping masks by simply dismounting an old mask and replacing with a new mask. Thereby, the charged particle beam exposure system of the present invention is not only useful in the BAA exposure system but also in the block exposure system.
Another object of the present invention is to provide a BAA exposure system capable of exposing a pattern on a large diameter substrate without increasing the size of the control system excessively.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a pattern on an object, comprising:
a base body for accommodating an object to be exposed;
a plurality of electron optical systems provided commonly on said base body, each of said electron optical systems including:
beam source means for producing charged particle beam, said beam source means emitting said charged particle beam toward an object on which a pattern is to be exposed, along an optical axis;
beam shaping means for shaping said charged particle beam to produce a plurality of charged particle beam elements in accordance with exposure data indicative of a dot pattern to be exposed on said object, said beam shaping means comprising a beam shaping mask carrying thereon a plurality of apertures for producing a charged particle beam element by shaping said charged particle beam;
focusing means for focusing said charged particle beam elements upon a surface of said object;
deflection means for deflecting said charged particle beam elements over said surface of said object; and
a column for accommodating said beam source means, said beam shaping means, said focusing means, and said deflection means;
said electron optical system thereby exposing said charged particle beam element upon said object held in said base body;
exposure control system supplied with exposure data indicative of a pattern to be exposed on said object and expanding said exposure data into dot pattern data corresponding to a dot pattern to be exposed on said object, said exposure control system being provided commonly to said plurality of electron optical systems and including memory means for holding said dot pattern data;
said exposure control system supplying said dot pattern data to each of said plurality of electron optical systems simultaneously, such that said pattern is exposed on said object by said plurality of electron optical systems simultaneously.
According to the foregoing embodiment of the present invention, the size of the BAA exposure system is substantially reduced, even when exposing a large diameter wafer by using a plurality of electron optical systems simultaneously.
Another object of the present invention is to provide a charged particle beam exposure system that uses an immersion electron lens, wherein the compensation of beam offset caused by the eddy current is successfully achieved with a simple construction of the electron optical system.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a pattern on an object by a charged particle beam, comprising:
a stage for holding an object movably;
beam source means for producing a charged particle beam and emitting said charged particle beam toward said object held on said stage along an optical axis; and
a lens system for focusing said charged particle beam upon said object held on said stage;
said lens system including an immersion lens system comprising: a first electron lens disposed at a first side of said object closer to said beam source means, a second electron lens disposed at a second, opposite side of said object, said first and second electron lenses creating together an axially distributed magnetic field penetrating through said object from said first side to said second side; and a shield plate of a magnetically permeable conductive material disposed between said object and said first electron lens, said shield plate having a circular central opening in correspondence to said optical axis of said charged particle beam.
According to the present embodiment as set forth above, the electric field inducted as a result of the eddy current is successfully captured by the magnetic shield plate and guided therealong while avoiding the region in which the electron beam passes through. Thereby, adversary effects upon the electron beam by the eddy current is effectively eliminated.
Another object of the present invention is to provide a charged beam exposure process capable of exposing both a BAA exposure process and a block exposure process on a common substrate.
Another object of the present invention is to provide a charged particle beam exposure system for exposing a pattern on an object, comprising:
a stage for holding an object thereon;
beam source means for producing a charged particle beam such that said charged particle beam is emitted toward said object on said stage along a predetermined optical axis;
a blanking aperture array provided in the vicinity of said optical axis for shaping an electron beam incident thereto, said blanking aperture array including a mask substrate, a plurality of apertures of identical size and shape disposed in rows and columns on said mask substrate and a plurality of deflectors each provided in correspondence to an aperture on said mask substrate;
a block mask provided in the vicinity of said optical axis, said block mask carrying thereon a plurality of beam shaping apertures of different shapes for shaping an electron beam incident thereto;
selection means for selectively deflecting said electron beam from said beam source means to one of said blanking aperture array and said block mask;
focusing means for focusing an electron beam shaped by any of said blanking aperture array and said block mask upon said object on said stage.
According to the construction of the present embodiment set forth above, it is possible to switch the BAA exposure and block exposure by using the single electron exposure system. Thereby, the addressing deflector, used in the block exposure process for selecting an aperture on the block mask, is used also as the selection beams for selecting the BAA exposure process and the block exposure process. Thereby, no extraneous fixture is needed for implementing the selection of the exposure mode.
Other objects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the attached drawings.